针对协作中继网络中目的端接收来自不同源节点发送的多个信息副本的合并方式，提出了联合非规则重复累积码与网络编码的改进译码算法. 首先对各链路的调制信息进行软解调处理，并根据中继处网络编码的异或信息和直达链路中原信息的函数对应关系，提取出协作节点发送到目的端的信息副本；然后更新非规则重复累积码在译码过程中直达链路与协作链路下的两个信息副本的软解调信息，构造出新的译码判决方法，进而推导了16QAM 软解调对数似然比值的简化方法；最后分析了系统的中断概率及频谱效率. 仿真结果表明，该译码算法在QPSK、16QAM两种调制方式下均能获得较低的误比特率，且采用对数似然比值的简化方法，能在0.3 dB 性能损失代价下降低系统的译码难度.
By combining multiple information copies from different source nodes at the destination node in a cooperative relay network, we propose a joint irregular repeat accumulate (IRA) code and network coding modified decoding (JI-NMD) algorithm. We first demodulate the modulation information with soft demodulation information of each link, and extract the information copies from the relay node at the destination. This is done according to the functional relationships between the network coding at relay node and the original information in the direct link. We then update the soft demodulation information
of the two copies from the direct and cooperative links in the IRA decoder, and construct a new decoding decision method. We further obtain a simplified log-likelihood ratio (LLR)method. Finally, we analyze the outage probability and spectral efficiency. Simulationresults show that the JI-NMD algorithm has lower bit error rate for QPSK and 16QAM.
[1] AHLSWEDE R, CAI N, LI S Y R, YEUNG R W. Network Information Flow [J]. IEEE Transactions on Information Theory, 2000, 46(4): 1204-1216.
[2] GUO Zheng, HUANG Jie, WANG Bing, ZHOU Sheng Li, CUI Jun Hong, WILLETT Peter. A practical joint network-channel coding scheme for reliable communication in wireless networks [J]. IEEE Transactions on Wireless Communications. 2012, 11(6): 2084-2094.
[3] ZHANG S, ZHUY, LIEW S, LETAIED Khaled Ben. Joint design of network coding and channel decoding wireless networks [C]// IEEE Wireless Communication and Networking Conference, 2007: 779-784.
[4] ZHANG S, LIEW S. Channel coding and decoding in a relay system operated with physical-layer network coding [J]. IEEE Journal on Selected Areas in Communications, 2009, 27(5): 788-796.
[5] LU L, LIEW S, ZHANG S. Optimal decoding algorithm for asynchronous physical-layer network coding [C]// IEEE International Conference on Communications, 2011: 1-6.
[6] 池新生，郑宝玉，姚刚，陈建白. 对称协作分集通信中网络编码的应用 [J]. 电子与信息学报，2012, 34(10): 2314-2319.
CHI Xin Sheng, ZHANG Bao Yu, YAO Gang, CHEN Jian Bai. The application of network coding in asymmetric cooperative diversity communication [J]. Journal of Electronics & Information Technology, 2012, 34(10): 2314-2319. (in Chinese)
[7] 高宏峰，许宗泽，吴援明. IRA码简化译码算法的研究[J]. 电子科技大学学报，2005, 34(1): 40-43.
GAO Hong Feng, XU Zong Ze, WU Yuan Ming. Reduced complexity decoding algorithms for irregular repeat accumulate codes [J]. Journal of University of Science and Technology of China, 2005, 34(1): 39-43. (in Chinese)
[8] 高宏峰.重复累积码及其在通信系统中的应用[M]. 北京：科学出版社，2008: 1-152.
GAO Hong Feng. The application of repeat accumulate code in communication system [M]. Beijing: Science Press, 2008:1-152. (in Chinese)
[9] HUANG Tao, YANG Tao, YUAN Jin hong, LAND Ingmar. Design of irregular repeat-accumulate coded physical-layer network coding for gaussian two-way relay channels [J]. IEEE Transactions on Communications, 2013, 61(3): 897-909.
[10] LI Zong Yan, PENG Mu Gen, WU Zhan Ji, WANG Wen Bo. Network coding scheme based on ldpc product codes in multiple-access relay system [C]// IEEE International Conference on Communications Workshops, 2011: 1-4.
[11] TOSATO F, BISAGLIA P. Simplified soft-output demapper for binary interleaved COFDM with application to HIPERLAN/2 [C]// Proceedings of IEEE International Conference on Communications, 2002: 664-668.
[12] CHEN Shao Lei, ZHANG Zhao Yang, Rui, YIN CHEN Xiao Ming, WANG Wei. Concatenated channel and network coding scheme for two-path successive relay network [J]. IET Communications, 2013, 7: 82-90.
[13] BHAT Uttam, DUMAN Tolga M. Decoding strategies at the relay with physical-layer network coding [J]. IEEE Transactions on Wireless Communications, 2012, 11(12): 4503-4513.
